Pinging: EGR Valve?

[chevychic]

How would I go about checking my EGR valve to determine if it's working properly? Also is the valve needed if all my smog components were removed and would a bad EGR valve cause pinging?

My truck is pinging heavily under load-actually it sounds like backfire but is too consistant like popcorn. It's to the point where I can't accelerate up hills or pass people on the freeway without it sounding like I'm chasing them down with a jar of marbles. It's like as soon as the secondaries open up, it chokes.

I've checked the timing with a light, reset the float in the carb as it was too high, adjusted the idle/mix using a vacuum gauge, replaced the fuel filter, cap, rotor, plugs and plug wires. Replaced the header gaskets and collector gaskets to rule out exhaust leaks. Now all is good and tight, and I still have the pinging.

The carb was rebuilt about 3 years ago so I don't think it's the culprit. All smog stuff has been removed by the PO.

I'm trying to start with the easy stuff before I go looking inside the engine.

This started suddenly after the truck had been sitting for about a year. I'd start it up and drive it a bit during this time, and it would start just fine but I didn't ever drive it long enough to burn off any junk that might have accumulated from sitting.

Now I'm driving it daily again while my firebird is in the shop and I'd like to get it back into shape.

Any ideas, suggestions?

EDIT: I did take a test drive with the vacuum advance line plugged to rule out the pickup coil. Not a bit of change.